Many people take nutraceuticals and supplements in the belief that they improve alertness or offset cognitive decline. Over the past decade or so there has been a large increase in the amount of research examining the links between diet, nutraceuticals and psychological function. This has revealed cognitive benefits from a number of sources. For example glucose administation improves cognitive functioning, and the mechanisms underlying this effect are increasingly understood. The glycaemic index (GI) of a food can also influence mental performance. There is also good evidence that certain dietary supplements have cognition-enhancing properties. These include endogenous substances which support neural structure and function (amino acids and polyunsaturated fatty acids). Other substances which improve cognitive fucntion appear to do so by increasing energy availability to the brain either directly (e.g. creatine) or via improving cardiovascular function (e.g CoQ10). Additionally certain herbal extracts can improve mood and cognitive function (in this chapter we use sage and lemon balm as examples). These effects are probably mediated by multiple actions including direct neurotransmitter modulation. Interestingly in the case of herbs, the behavioural effects are often in keeping with their usage in traditional medicine systems. There are numerous challenge in understanding the effects of nutraceuticals on cognition. As well as the issue of standardisation, there is the problem of understanding the mechanicsims and underlying effects which involve multiple proceses. These challenges are increasingly being met by new technologies which enhance our understanding of brain functioning.